Fluorescent particles have a broad application in tagging, tracing, and labeling (Hasegawa et al., 2005, Edwards et al., 2004, Lizard et al., 2004, Meldal, 2002, and Ohata et al., 2003). Fluorescence is typically made through incorporating either inorganic or organic fluorescent dyes into the particle's material. While inorganic dyes are typically more stable, their number and compatibility is rather restricted. A large variety of organic dyes makes them attractive for creating fluorescent particles. However the problems are in the dye's stability and its typically high toxicity. Incorporation of dyes into silica matrix seems to be one of most promising approaches because of excellent sealing ability of silica and wide compatibility of silica with other materials. Numerous attempts to embed organic dyes into silica xerogels and zeolites have been known for long time (Rao and Rao, 2003, Klonkowski et al., 2002, Deshpande and Kumar, 2002, Leventis et al., 1999, del Monte and Levy, 1998, Suratwala et al., 1998, Calzaferri et al., 2003, Ow et al., 2003, Zhao et al., 2004, Santra et al., 2004). To prevent leakage of the dyes out of the porous matrix, dyes were covalently bound to the silica matrix (Frantz et al., 2002, Leventis et al., 1999, Baker et al., 1999, Suratwala et al., 1998, Lin et al., 2005). While the photo stability of such materials was higher than stability of pure dyes, it did not prevent bleaching substances, including oxygen, from penetration inside such a composite material.
Fluorescent particles are widely manufactured, but the processes used for their production are often tightly held trade secrets. So far the brightest particles have been made of quantum dots incorporated into polymer matrix (Han, et al. 2001), the case of micron size particles, or quantum dots themselves, and the case of nanometer size particles. Incorporation of dyes and quantum dots into glass particles seems to be one of most promising approaches because of excellent sealing ability of the glass and wide compatibility of glass with other materials.